Creating a New Internal Door

Hi, I'm looking for some advice please. I'm looking at knocking a separate bathroom and toilet into one bigger room. I want to go from A to B.



I'm fairly sure the wall between the 2 isn't supporting, it's running the same way as the joists and it's just a wooden frame covered by plaster and lathe. I want to remove about half of that.

I want to remove the 2 doors and frames and replace that with one door as shown in B.

I plan to buy a new wooden door frame kit from B&Q. My question is, when I position new king stud on the right side of the frame and a new top plate, will I need to cut out the plaster or can I fix straight through the plaster and lathe. The wall on the right under the plaster is brick and I'd be fixing to the nearest joist above for the top plate. I'm just hoping to avoid cutting large sections of the plaster and lathe.

Any help and guidance appreciated.

I guess all I'm really asking is whether I can secure the new door frame to through plaster to the brick wall. Or do I need to hack the plaster away and secure directly to the brick?

You certainly can fix directly to the plaster, use heavy (8mm min dia) hammer hits driven 50mm into the solid brick, which will provide almost self support i.e. not relying on the plaster at all...pinenot